2967: Matter

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Matter

Title text: He was the first person to land a 900, which is especially impressive because pulling off a half-integer spin requires obeying Fermi-Dirac statistics.

Explanation

In skateboarding, the term "goofy" refers to a skater using the goofy stance, with the skater's right foot at the front of the board and left foot at the rear. This is backwards from how most right-handed people feel most natural when stepping on a skateboard. In this comic, famed professional skateboarder Tony Hawk, who skates goofy-footed, has obtained a professorship in physics and is teaching about antimatter in particle physics, which has the opposite electrical charge of corresponding matter particles that will annihilate each other upon collision, releasing energy proportional to their combined mass. As Tony Hawk does not have a degree in physics,^{[citation needed]} teaching inaccurate or very non-standard lessons such as this one could be a likely pitfall of his gaining a professorship in real life. Hawk is also the subject of 296: Tony Hawk.

Unlike other distributions of 'handedness' in the natural world (chemical chirality, or the skewness of bimodal statistics describing asymmetries in nature called homochirality), 'goofy-footed' skateboarders are about as common as those using standard footing. Thus the analogy indirectly raises the issue of baryon asymmetry, the observation that ordinary matter is very much more common than antimatter because there is so little evidence of annihilation throughout the universe. Baryon asymmetry is often thought to have resulted from fluctuations during cosmological inflation between 10⁻³³ and 10⁻³² seconds after the Big Bang, although there are several other candidate explanations of varying falsifiability.

The title text describes Hawk as the first person to "land a 900," meaning the successful completion of a skateboarding trick that involves two and a half rotations (nine hundred degrees, as 2.5 × 360° = 900°). In physics, spin is a quantum number describing subatomic particles (see 1862: Particle Properties), named in reference to the vaguely analogous but crucially distinct concept of angular momentum in classical physics. Obeying Fermi–Dirac statistics requires that the particles involved are fermions, which include all of the electrons, protons and neutrons that compose the entirety of everyone's body and electrochemical state. Fermions all have half-integer (i.e., ...–1½, –½, ½, 1½...) spin quantum numbers which do indeed include 2½, but only extremely rare particles have a spin of 5/2. However, it's very important to remember that quantum mechanical spin is not rotation, but instead how quickly the corresponding particle changes state when rotated.

While everyone (and almost everything we ordinarily interact with except light and cosmic rays) is composed entirely of fermions, any composite particle made of an even number of fermions, including entire atoms and their nuclei, are not fermions but bosons, which do not obey Fermi–Dirac statistics. Luckily, landing a 900 does not actually require obedience to Fermi–Dirac statistics because a skateboarder composed entirely of bosonic atoms would still have fermionic electrons in the orbitals of those atoms and thus would still obey the far more macroscopically fundamental and consequential Pauli exclusion principle. That principle gives atoms and molecules, which are almost entirely empty space, tangible presence and material form, allowing us to hold things, walk, make sound waves with our voices, employ any mechanical property of matter, and allowing sufficiently skilled skateboarders to land a 900.

Transcript

[Tony Hawk (drawn with short hair) is gesturing at a narrow whiteboard on which illegible things are marked, what may be a Feynman diagram with one of the particle/antiparticle pair going into a circle (possibly representing a black hole, and thus depicting the popularized (incorrect) analogy for Hawking radiation), and at the bottom, a 2x3 table of illegible values.]

Tony Hawk: In the standard model, regular matter will annihilate if it comes in contact with oppositely-charged goofy matter.

[Caption below the panel:]

Tony Hawk becomes a physics professor

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Discussion

This one is a head-scratcher. Do skateboarders call "anti-" things goofy? What's the deal with that Dirac statistic? 162.158.154.31 23:47, 2 August 2024 (UTC)

It's like being a 'southpaw' boxer (or at least being able to stand the opposite way, maybe in order to flip/spin the board the opposite way from what you would end up kicking it normally).

The Dirac thing is... well, quantum physics has various uses/restrictions upon spin (and colour, etc) that isn't really physical spin (or colour) as we know it, but sort of means a kind of particle-based rotational momentum, which has to be conserved/transfered/agree in various quantum interactions (and is a quantised state, meaning that only certain spin-values can exist in a given situation).

Both the skateboarding and the elementary physics issues are (in their own way) rather technical matters, and I know a lot more about one than the other (but think I understand the other a lot more, from just reading up on it, than I know I actually understand the original one based on what I actually was taught). 172.70.162.186 00:03, 3 August 2024 (UTC)

"Do skateboarders call "anti-" things goofy?" FWIW, I first heard 'goofy' in the 1960s skateboard fad, using your left foot where the right foot normally goes. It appears this was 2 or 3 years before Mr Hawk was born, so it isn't his invention. I would wonder if surfers (Hawaii and California) got goofy even earlier. PRR (talk)

Looks like a fair summary: Goofy Foot --PRR (talk) 02:21, 3 August 2024 (UTC)

I first heard the term "goofy foot" back in Skate or Die on the NES. 162.158.212.133 07:59, 3 August 2024 (UTC)

I'm way over the hill, and that linked 20 minute video on spin was the first explanation of that quantum number which seemed fully satisfactory and didn't leave me feeling like I was missing something crucial. https://www.youtube.com/watch?v=pYeRS5a3HbE&t=18m30s "The spin number characterizes how fast the state of a particle changes when we rotate it in space." WHERE HAS THAT EXPLANATION BEEN ALL MY LIFE?!?! 172.68.22.90 04:56, 3 August 2024 (UTC)

Spin is a terrible name, it should be "twist factor" for example. It's a derivative unit error, like calling acceleration in terms of speed. 162.158.90.198 07:58, 3 August 2024 (UTC)

I second both of those comments. 108.162.245.66 02:27, 6 August 2024 (UTC)

Problem loading previous comic, I get MediaWiki error. SDSpivey (talk) 17:15, 3 August 2024 (UTC)

Can't replicate that, and doesn't sound like the kind of errors I might get (504s, "sorry too busy"-style message, etc). Is it still happening for you? 172.70.85.18 19:23, 3 August 2024 (UTC)

I get this

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MediaWiki internal error.

Original exception: [Zq_L66Th-kkFBgrsnjHznwAAAEQ] 2024-08-04 18:43:55: Fatal exception of type "MWException"

Exception caught inside exception handler.

Set $wgShowExceptionDetails = true; at the bottom of LocalSettings.php to show detailed debugging information.

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Only on Firefox, Opera loads fine. Other pages seem to load fine also. It only happens on 2966, whether I go from 2967 or 2965, or if I try to manually enter URL. The letters in the brackets do change each time.SDSpivey (talk) 18:52, 4 August 2024 (UTC)

A quick search for the error indicates old errors that (ten years ago) say "I know this is an old issue, but...", and it looks like we need a server admin to add the detailed debugging thing to work for you.

Tested here with Chrome (Android), Firefox (Android) and Firefox (Windows). No problem when going to 2966 through the respective Previous/Next buttons from neighbours. No problem with going there 'directly', in several different ways, to 2966 (which redirects). Nor Exam Numbers (which also redirects) nor 2966: Exam Numbers (to which everything redirects). Do any of these non-Next/Previous links work/not work if you jump off from here?

This is just from my basic 'no login' connection. Does it error if you aren't logged in to your SDSpivey account? (Maybe you don't login through Opera, but do in Firefox? You'd know that better. If that's the case, it's maybe something funny within in your own profile configuration, like a server-stored 'skin' or 'filter' error/incompatibility of some kind.) The fact that nobody else is reporting trouble makes me think it's you-specific, but it doesn't sound like it's a browser-side issue. Grasping at straws here, but covering my best ideas at this time. 172.69.43.227 20:36, 4 August 2024 (UTC)

This part doesn't make any sense to me; was this section AI generated? "That is why it is very difficult to compress matter based on fermions and even to get goofy matter (which are not identical particles), as they should be brought in contact with in the comic, near enough or mixed enough with the normal matter." ProphetZarquon (talk) 21:15, 3 August 2024 (UTC)

Reverted as an incorrect and confusing attempt to extend the panel joke into the title text explanation. That never goes well. 172.71.150.237 21:47, 3 August 2024 (UTC)

So in skateboard, does goofy just mean "left foot" or does it mean "non-dominant foot". Like, would a left handed skater be skating goofy "normally", or is goofy for them, using right foot?

Left, because it's described in the frame of reference of observers. 172.70.214.34 07:35, 4 August 2024 (UTC)

So if I'm a left-handed observer, then are right-handed skaters goofy? PotatoGod (talk) 12:14, 5 August 2024 (UTC)

Only if they're doing a handstand while riding it.172.69.195.5 14:15, 5 August 2024 (UTC)

Goofy is specifically right foot forward, kicking with your left. The other way round is 'regular'. 'Goofy' and 'Regular' are used to denote your normal stance. That is, the way you skate most comfortably. Skating the opposite way round to your normal stance is called 'fakie'. This can be different for different skaters. 'Fakie' for someone who skates 'Regular' would be 'Goofy', and vice versa 172.69.43.185 09:13, 6 August 2024 (UTC)

Have made a new Category:Skateboard. There have for a long time been one for Electric Skateboard but I found 10 with regular skateboards being referenced. --Kynde (talk) 09:08, 4 August 2024 (UTC)

The extra spacing in the Feynman diagram on the blackboard explains why most antimatter was annihilated. 172.69.135.89 10:00, 4 August 2024 (UTC)

Given an initial universe with equal parts matter and antimatter plus a slight asymmetry (50% + e), the mutual annihilation of matter and antimatter would leave behind a residual amount of matter proportional to the asymmetry e. In the extremely dense early universe, this annihilation would be nearly complete, ensuring that almost all antimatter and a corresponding amount of matter would be annihilated into energy, leaving an excess of matter. Thus, the observed baryon asymmetry today can be explained by this initial slight asymmetry, as even a minuscule e would result in a predominantly (anti)matter-filled universe post-annihilation. 172.70.210.52 10:33, 4 August 2024 (UTC)

It does mean that mass-energy conservation (or ways to feed that energy into other things, e.g. the expansion of space itself?) gives us a different initial distribution to the kind of initial universe where the imbalance was never just a residual (anti-particals just naturally being rarer to find/be created), and still begs the question of where such an imbalance came from (however small) from a spontaneously created universal 'seed' that one would imagine ought to be 'property neutral' in combining all essentially symmetric measures. But I added a little something about this to my own edit. (My edit being an attempt to stop huge run-on sentences with comma asides (and other dubious usages of comma), in a key section. So much so that I gave up trying to work out what some of it was intended to mean and just gave my own version. Still with plenty of commas, but not relying quite so heavily upon them alone.) 172.69.195.231 11:53, 4 August 2024 (UTC)

No, it does not. 172.70.207.39 14:22, 4 August 2024 (UTC)

What is wrong there? (I can see some messy understanding, but there's also some practical correctness.) What (especially with the changes to remove, loads, of, long, comma-ey, back, and, forth, sentences; it definitely does need rewriting, as it now is again!) required the whole lot reverting? 172.70.86.38 18:12, 4 August 2024 (UTC)

I reverted https://www.explainxkcd.com/wiki/index.php?title=2967:_Matter&diff=348077&oldid=348076 because reality. 172.69.22.196 13:06, 4 August 2024 (UTC)

My working title for my skateboarding game where you pull tricks off of an undulating gravity wave surface is "Tony Hawking". (Ben Newman) 172.70.231.38 18:31, 5 August 2024 (UTC)

Remember: If the gameplay has you going round a half-pipe with a skateboard, the inspiration is probably Tony Hawk's. If it has you going round a country with a fridge, the inspiration is probably Tony Hawks'... 172.70.91.141 18:46, 5 August 2024 (UTC)

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The first sentence is incorrect, "goofy" refers to a skater's stance on the board and has nothing to do with which foot is used to push. The term "Mongo" is used to describe when a skater pushes with their front foot, so it's entirely possible to have a skater who uses a goofy stance while pushing mongo. I haven't edited the page because I'm new here and not sure what I'm doing (hi) but I'll paste here how I tentatively reworded the first sentence to be more correct and provide more information. Also Tony Hawk himself skates goofy, which feels noteworthy given the context of this comic. "In skateboarding, the term "goofy" refers to a skater using the goofy stance, with the skater's right foot at the front of the board and left foot at the rear. This is backwards from how most right-handed people feel most natural when stepping on a skateboard. Notably, Tony Hawk himself skates Goofy-footed." 172.70.39.205 14:13, 8 August 2024 (UTC)

✓ Done 172.70.211.234 05:21, 15 August 2024 (UTC)

Are we sure "goofy" matter does not also refer to "strange matter"? https://en.wikipedia.org/wiki/Strange_matter 172.71.103.15 (talk) 08:59, 9 August 2024 (please sign your comments with ~~~~)